Soybean is a legume crop enriched with proteins and oil. It is frequently exposed to anthropogenic and natural flooding that limits its growth and yield. The current study applied gel-free proteomic techniques to unravel soybean response mechanisms to flooding stress. Two-day-old soybeans were flooded for 4 days continuously, and root samples were collected on days 2 to 6 for proteomic and enzymatic analyses. Age-matched untreated soybeans were collected as a control. After protein extraction, purification, and tryptic digestion, the peptides were analyzed on nano-liquid chromatography-mass spectrometry. A total of 539 and 472 proteins with matched peptides 2 or more were identified in control and flooded seedlings, respectively. Among these 364 proteins were commonly identified in both control and flooded soybeans. Fourty-two protein’s abundances were changed 4-fold after 2-days of flooding stress as compared to starting point. The cluster analysis showed that highly increased proteins included cupin family proteins, enolase, pectin methylesterase inhibitor, glyoxalase II, alcohol dehydrogenase, and aldolase. The enzyme assay of enolase and pectin methylesterase inhibitor confirmed protein abundance changes. These findings suggest that soybean adopts the less energy-consuming strategies and brings biochemical and structural changes in the cell wall to effectively respond to flooding stress and for survival.